Conventionally, transparent resins are used as the materials for molded products which typically require transparency such as automobile components, illumination equipment and electrical components. Particularly in recent years, the application of these resins as optical materials, in which the optical properties are important, continues to progress. Examples of known transparent resins which can be ideally applied to such applications include polycarbonate-based resins and acrylic-based resins. However, although acrylic-based resins offer excellent transparency, they have problems in terms of heat resistance and water resistance. In contrast, polycarbonate-based resins offer superior performance to acrylic resins in terms of heat resistance and water resistance, but suffer from different problems such as a high birefringence.
As a result, recently, cyclic polyolefin-based resins which combine transparency, water resistance (low water absorption), a low birefringence, and heat resistance have started to be used as the transparent resins for optical materials.
Polymers synthesized using cyclic olefins as monomers are amorphous due to the presence of bulky alicyclic structures on the principal chain skeleton, display excellent transparency and heat resistance, and moreover also offer other characteristics such as little optical distortion, low water absorption, acid and alkali resistance, and a high level of electrical insulation, and consequently they have been developed for display applications (such as retardation films, diffusion films, liquid crystal substrates, films for touch panels and light guide plates), optical lens applications, optical disk applications (such as CD, MD, CD-R and DVD), optical fiber applications, optical film/sheet applications, optical semiconductor sealing applications, printed wiring board applications (such as rigid printed wiring boards, flexible printed wiring boards and multi layer printed wiring boards), and as substrates for transparent conductive films. Amongst such cyclic olefins, development has centered around cyclic olefin-based polymers with highly reactive norbornenes as precursors.
Cyclic olefin-based polymers such as those described above are typically converted to products by fabrication using molding methods such as injection molding and molten extrusion molding, although with conventional cyclic olefin-based polymers, the birefringence which develops due to the polymer orientation during the molding process has not always satisfied the demanded characteristics, and as a result, the optical characteristics of the generated optical product also failed to meet the demanded characteristics. With the improvements in electronic technology in recent years, the development of a material which retains the excellent transparency and heat resistance characteristics of conventional cyclic olefin-based polymers, but enables a reduction in the birefringence which develops due to the polymer orientation has been keenly sought, although until now, such a material had yet to be discovered.